Multiple Choice
Which statement best describes the difference between a neutral element and an ion?
2. Atoms & Elements
Ions
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Which ion has the same electron configuration as an atom of He?
A
Li+
B
H−
C
F−
D
Na+
Verified step by step guidance1
Recall that the electron configuration of a neutral helium (He) atom is $1s^2$, meaning it has 2 electrons.
To find an ion with the same electron configuration as He, look for ions that have 2 electrons in total, regardless of their nuclear charge.
Consider each ion: Li$^+$ means lithium has lost one electron, so it has 3 (atomic number) - 1 = 2 electrons, matching He.
H$^-$ means hydrogen has gained one electron, so it has 1 (atomic number) + 1 = 2 electrons, also matching He.
F$^-$ and Na$^+$ have more or fewer electrons than 2, so they do not share the same electron configuration as He.
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